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VIETNAM NATIONAL UNIVERSITY, HA NOI VNU UNIVERSITY OF SCIENCE FACULTY OF PHYSICS  Pham Thi Que COMPREHENSIVE QUALITY ASSURANCE FOR RADIATION ONCOLOGY Submission of a partial fulfillment of the requirement for the degree of Bachelor of Science in Physics (Advanced Program) Hanoi, 2017 VIETNAM NATIONAL UNIVERSITY, HA NOI VNU UNIVERSITY OF SCIENCE FACULTY OF PHYSICS  Pham Thi Que COMPREHENSIVE QUALITY ASSURANCE FOR RADIATION ONCOLOGY Submission of a partial fulfillment of the requirement for the degree of Bachelor of Science in Physics (Advanced Program) Supervisor: Nguyen Xuan Ku, MSc Hanoi, 2017 ACKNOWLEDGEMENT First of all, I would like to express my deep gratitude to my research supervisor, Master Nguyen Xuan Ku for his kind guidance, endless support and the great adviser to me I would like to thank him for encouraging me and giving me opportunity to the research on this topic, which also helped me to know about many new things His advices are priceless on my both research as well as my future career Secondly, I always appreciate all teachers, lectures, researchers and other seniors in Faculty of Physics, particularly Department of Nuclear Technology, VNU University of Science, Vietnam National University for creating good conditions for students like us to work and experience And finally, I want to give my special thanks to my family and friends who have supported me in not only my research but also my whole studying They have become my strong motivation to pass through the hard time Student, Pham Thi Que Comprehensive QA for Radiation Oncology LIST OF ABBREVIATION AAPM American Association of Physicists in Medicine ADCL Accredited Dosimetry Calibration Laboratory BEV Beam’s-eye-view CT Computerized Tomography DVH Dose Volume Histogram HDR High Dose Rate ICRU International Commission on Radiation Units and Measurement ISCRO Institutional Stem Cell Research Oversight Committee JCAHO Joint Commission on the Accreditation of Health Care Organization LDR Low Dose Rate MLC Multileaf Collimator MRI Magnetic Resonance Imaging MU Monitor Unit/Minute NIST National Institute of Standard and Technology PDD Percent Depth Dose QA Quality Assurance QAC Quality Assurance Committee R&V Record and Verify SAD Source Axis Distance SSD Source Surface Distance TLD Thermoluminescent Dosimeter TMR Tissue Maximum Ratio TPR Tissue Phantom Ratio 3D Three-dimension Comprehensive QA for Radiation Oncology Table of contents PART A: INFORMATION FOR RADIATION ONCOLOGY ADMINISTRATORS Radiation Oncologist Radiation Oncology Physicist 3 Radiation Therapist 4 Medical Radiation Dosimetrist PART B: CODE OF PRACTICE CHAPTER 1: COMPREHENSIVE QA PROGRAM 1.1 Introduction 1.2 QA Committee 1.3 Comprehensive QA Team 1.4 Policies and Procedures Manual 1.5 Quality Audit 1.6 Resources and Continuous Quality Improvement CHAPTER 2: QA OF EXTERNAL BEAM RADIATION THERAPY EQUIPMENT 2.1 QA of Medical Electron Accelerators 2.2 QA of Simulators 10 2.3 QA of CT Scanners 10 2.4 QA of Measurement Equipment 11 CHAPTER 3: TREATMENT PLANNING COMPUTER SYSTEM 12 3.1 Program Documentation 12 3.2 Test Procedures 12 CHAPTER 4: EXTERNAL BEAM TREATMENT PLANNING 14 4.1 Treatment Planning Process 14 4.1.1 Prescription 14 4.1.2 Positioning and Immobilization 15 4.1.3 Data Acquisition 15 Comprehensive QA for Radiation Oncology 4.1.4 Contouring 15 4.1.5 Data Transfer 16 4.1.6 Target volume and Normal Organ Definition 16 4.1.7 Aperture Design 16 4.1.8 Computation of Dose Distributions 17 4.1.9 Plan Evaluation 17 4.1.10 Computation of Monitor units 17 4.1.11 Beam modifiers 18 4.1.12 Plan Implementation 18 4.2 Treatment Planning QA for Individual Patient 19 4.2.1 Treatment Plan Review 19 4.2.2 Monitor Unit Calculation Review 19 4.2.3 Plan Implementation 19 4.2.4 In Vivo Dosimetry 20 CHAPTER 5: BRACHYTHERAPY 22 5.1 Sealed Sources 22 5.1.1 Description of Sources 22 5.1.2 Calibration of Sources 23 5.1.3 Brachytherapy Source Calibrators 25 5.1.4 Brachytherapy Applicators 27 5.1.5 Source Inventories 28 5.2 Treatment Planning and Dosimetry 29 5.2.1 Planning 30 5.2.2 Localization 30 5.2.3 Dose Calculation Algorithms 30 5.2.4 Patient Dose Calculation 31 5.2.5 Delivery of Treatment 31 5.2.6 Documentation 31 5.3 Remote loading 32 Comprehensive QA for Radiation Oncology 5.3.1 Calibration 32 5.3.2 Verification of Source Position 32 5.3.3 End effects 33 5.3.4 Safety 33 CHAPTER 6: QA OF CLINICAL ASPECTS 34 6.1 New Patient Planning Conference 34 6.2 Chart Review 34 6.3 Chart Check Protocol 35 6.3.1 Review of New or Modified Treatment Field 35 6.3.2 Weekly Chart Review 35 6.4 Film Review 36 6.4.1 Portal Images 36 6.4.2 Ongoing and Verification Images 36 CONCLUSION 37 REFERENCES 38 Comprehensive QA for Radiation Oncology List of Table Table 1: The performance tests, tolerances, frequencies of medical electron accelerators Table 2: The performance tests, tolerances, frequencies of simulators 10 Table 3: The performance tests, tolerances, frequencies of measurement equipment 11 Table 4: QA for treatment planning systems and monitor unit calculations 13 Table 5: Factors effecting monitor unit (minute) calculations 17 Table 6: Summary of QA recommendations for individual patients 20 Table 7: Source QA tests and their frequency and tolerances for brachytherapy source calibrator 25 Table 8: The QA tests for brachytherapy source calibrator 25 Table 9: QA tests for brachytherapy applicators 27 Table 10: Procedure specific parameter verification 31 Table 11: QA of remote afterloading brachytherapy units 32 Comprehensive QA for Radiation Oncology PREFACE Nowadays, the frequency of cancers in the Asia-Pacific region has increased essentially over the past several years If the projection is right, the quantity of cancer cases in Asia is set to increase from 3.5 million in 2002 to 8.1 million by 2020 if the current management strategies are not changed And Vietnam is not an exception According to statistics of K Hospital and Oncology Hospital-HCM City, there are 75.000 people died because of cancer and 120.000 to 150.000 people who are diagnosed getting cancer every year Therefore, radiotherapy plays an important role in the treatment of cancer Beside of the treatment process, the quality assurance in radiation oncology is important too However, the QA program in radiation oncology has not been set in all treatment facility in over our country This happened because of lacking fully aware about the issue importance, funding, investment or because radiation oncology members have not trained in a basic way Now, it is time for us to treat quality as the primary goal and QA program is concerned In order to have a comprehensive look about QA program, I figure out the topic named “Comprehensive QA for Radiation Oncology” This thesis includes parts: part A is for administrators, and part B is a code of practice in six chapters The first chapter of part B describes a comprehensive QA program in which the importance of a written procedural plan administered by a multidisciplinary committee is stressed The second chapter of part B concerns QA of external beam therapy equipment The third chapter describes QA for treatment planning computers The fourth describes the treatment planning process and QA procedures for individual patients The fifth considers the new details of source strength and emphasizes the use of redundant systems for source strength calibration and checking The sixth part is the most clinical and discusses new patient conferences, film review, chart review, and a detailed protocol for chart checking Comprehensive QA for Radiation Oncology PART A: INFORMATION FOR RADIATION ONCOLOGY ADMINISTRATORS Delivery of treatment in an accurate and predictable way is not easy to achieve, because the radiation therapy process is a complex interweaving of number of related tasks for designing and delivering radiation treatments It includes a determination of the extent of the disease and a determination of patient’s particular parameters (e.g surface anatomy, internal organs, and tissues including the tumor) in order to determine the size, extent and location of the tumor (target volume) Then, the intended radiation dose distribution is calculated by software algorithms of a treatment planning system To treat the patients as planned requires accurately calibrated treatment unit, the accessibility of treatment aids and immobilization gadgets for positioning and maintaining the patient in the planned position The International Commission on Radiation Units and Measurements has recommended that the dose be delivered to within 5% of the prescribed dose [12] If there are many steps required in delivering dose to a target volume, each step must be performed with an accuracy much better than 5% to achieve the ICRU recommendation But in reality, it is difficult to evaluate an accuracy and consistency estimate required in each step To meet such standards required the availability of important facilities and equipment including treatment and imaging units, radiation measuring devices, computer treatment planning systems and the appropriate staffing levels of qualified radiation oncologists, radiation oncology physicists, dosimetrists, and radiation therapists Furthermore, the increasing of the complexity of treatment modalities can lead to the increase of expectations on the quality of treatment, which makes QA procedures more complex To cope with this situation, it is important that QA processes and procedures emanate from a QA committee This committee always draws its immediate authority from the administrator of the departure of radiation oncology The members of the QA committee should include a representative Comprehensive QA for Radiation Oncology manufacturer’s data more than 3%, the source of difference should be investigated Table 7: Source QA tests and their frequency and tolerances for brachytherapy source calibrator [3] With I, initial purchase; D, documented; and E, at every use 5.1.3 Brachytherapy Source Calibrators In principle, source strength can be measured with a variety of detectors such as well ionization chamber or thimble chamber Well ionization or reentrant chambers are favored for conventional strength brachytherapy sources, and thimble chambers measuring radiation intensity at a distance are favored for high dose rate sources However, thimble chambers have been utilized effectively for conventional dose rate sources and reentrant chamber was designed for high dose rate sources And the QA tests for this calibrator are listed in Table 25 Comprehensive QA for Radiation Oncology Table 8: The QA tests for brachytherapy source calibrator [3] With I, initial use or following malfunction and repairs; S, isotope/source specific; D, documented and correction applied or noted in report of measurement; E, each us or ongoing evaluation a Commissioning a Calibrator QA tests for commissioning a calibrator include precision, scale factors and linearity, ion collection efficiency, geometry and length dependence, energy dependence test The precision of the source calibrator should be better than 2% and the signal-to-noise ratio greater than 100: l The scale factor and linearity of each scale used on the electrometer should be determined and monitored Ion collection efficiency should be better than 99% for commercial well chambers and conventional brachytherapy sources The relative orientation of the source axis is vital for any calibrator because of dose anisotropy about a source In this way, a source ought to be moved through the active volume of the chamber to confirm and evaluate the extent of the change in sensitivity with source position The sensitivity of well ionization chambers relies on the energy of the photons, even in “airequivalent” or “tissue-equivalent” chambers And the calibration of thimble chamber may also change with the photon energy 26 Comprehensive QA for Radiation Oncology b Redundancy A redundant system is a collection of radiation sources and detectors whose radiologic characteristics are predictable with a high level of reproducibility A two-component brachytherapy source calibration redundant system includes isotope calibrator and a long half-life encapsulated radioactive source or a calibrator and the manufacturer’s source specification A three-component redundant system is a major improvement, since the third component of the system can resolve the differences between the other two Several three-component systems are: a radionuclide calibrator, a standard source of the radionuclide in question and a second long half-life reference source of another radionuclide; or a standard radionuclide calibrator, a reference long half-life source and a second radionuclide calibrator (preferably of different design from the standard); or a radionuclide calibrator, a reference long half-life source and the manufacturer’s source specification Four-component (or more) systems can be built up by adding more calibrators or more sources (ideally of different radionuclides) An institution should maintain at least a two-component redundant system A three-component redundant system is favored, because it is easier to identify the origin of a discrepancy A three-component redundancy system is recommended for newly developed isotopes for which no standards exist 5.1.4 Brachytherapy Applicators Table lists QA tests to be performed for brachytherapy applicators In this table, I, initial use or following malfunction and repairs; D, documented and correction applied or noted in report of measurement; E, as a minimum, a visual inspection to verify that the dummy sources fairly represent the active source distribution Table 9: QA tests for brachytherapy applicators [3] 27 Comprehensive QA for Radiation Oncology 5.1.5 Source Inventories Because of the difference between information and procedure, both long and short half-life sources require both an active inventory and a permanent file a Long half-life sources The active inventory ought to be posted in the hot lab, and maintained in the dosimetry section for calculation purposes The inventory should consist of: + Radionuclide and type of source + Total number of sources and total source strength + For each group of comparable sources: number of sources, mean source strength/ spread in source strength, date appropriate/time period in use clinically, institution’s identification, safe location A permanent file ought to be maintained containing the following information: + Radionuclide, manufacturer, type of source, model number or other description + Diagrams delineating all materials and dimensions of the source + For each source or group of comparable sources: institution’s verification of manufacturer’s calibration/date, leak test results, location in institution b Short half-life sources The active inventory should contain radionuclide, batch identification, and source strength, total source strength and source strength per 28 Comprehensive QA for Radiation Oncology seed/wire/source train A permanent file should consist of the following information for the same period of time required for the patient’s treatment records: + Radionuclide, manufacturer, type of source, model number or other identification + Batch number, number of seeds or wires, date of shipment + + Date appropriate and manufacturer’s source strength specification Number of seeds per ribbon/number of wires or seed ribbons + + Weighting/Seed spacing Institution’s confirmation of manufacturer’s calibration + Wipe test record + Disposal: date return to the manufacturer or location in long term storage c In-use Inventory There should exist a log for both long and short half-life sources currently utilizing as a part of treatment This log should include: + + Patient’s name, procedure and date, room number Responsible person and phone number + + + Number of sources and total source strength Attending doctor Source disposal 5.2 Treatment Planning and Dosimetry In brachytherapy, two calculations are often required in order to avoid that the execution of treatment can deviate from treatment planning They are planning calculations to determine the distribution and activity of sources, and verification calculations to determine the treatment time from the actual distribution of sources Permanent implants require careful planning because the number and strength of sources are determined by the implant’s volume In addition, the implant cannot be modified after implantation Furthermore, timing is also very important for short half-life sources (e.g Au-198 decays 1% per hour, while I-125 decays 1% per day) 29 Comprehensive QA for Radiation Oncology 5.2.1 Planning The basic aim of planning is to achieve a dose distribution that will treat the target volume without exceeding normal tissue tolerance Therefore, all implants should be planned From this plan, basic implant parameters such as source type, number of sources, length, spacing and special devices needed are obtained Traditional systems such as Manchester (Meredith, 1967), Quimby (Quimby and Casto, 1953), Paris (Pierquin et al., 1978), Stockholm (Walstam, 1954) can still be very useful as a planning tool although computerized calculations are now relatively standard in planning brachytherapy procedures 5.2.2 Localization Excepting radioactive eye plaques and other surface plaques, the location of all intracavitary, interstitial implants, including vaginal applicators should be verified by radiography or CT Orthogonal and stereo-shift X-ray techniques are the most regular methods for source and tissue localization Dosimetry personnel should be present during the localization of implant to guarantee that the proper geometry is maintained Dummy sources utilized for these studies should simulate source position and spacing accurately At least, a visual check is recommended to verify that the dummy sources fairly represent the active source distribution 5.2.3 Dose Calculation Algorithms In most treatment planning program, source strength is specified as exposure rate at a distance, equivalent mass of radium, apparent activity, not as air karma rate at a large distance Because source calibration is air karma rate at a point far from the source, it is important to confirm that the calculational algorithm properly converts this source calibration into the proper dose distribution near the source for treatment planning programs 30 Comprehensive QA for Radiation Oncology 5.2.4 Patient Dose Calculation Post-implant dose distributions should be calculated in a timely manner The dose distribution should be calculated in three planes to establish the three-dimensional nature of the distribution As with external beam dosimetry, it is necessary to review all patient dose calculations in order to verify and correct serious errors before treatment is complete 5.2.5 Delivery of Treatment The final consideration for QA is to guarantee the delivery of the treatment to the patient Documentation of the physical parameters is necessary for this QA to verify how the implant is to be loaded (e.g source strength, applicators, dimensions of implant, dose prescription, implant time, etc.) Furthermore, unambiguous communication lines should be established to transfer the necessary information among members of the implant team Table 10 describes a number of steps in the execution of brachytherapy treatment Physicists should be present in the operating room during custom planned procedures and challenging dosimetric problems Table 10: Procedure specific parameter verification [3] 5.2.6 Documentation A written dosimetry report for each brachytherapy procedure is 31 Comprehensive QA for Radiation Oncology recommended to be inserted in patient’s charts The report should contain: sources description, description of technique and source pattern used, time of dose delivery, the total air karma strength, description of the dose (e.g prescribed dose, dose at the border of the target volume, a central dose, regions of high or low dose, etc.), isodose distribution, dose volume histograms, quality indices, etc [14] 5.3 Remote loading Remote loading systems include conventional low dose rate (LDR) as well as high dose rate (HDR) devices [7] At this part, three principle QA end points is presented, they are accuracy of source selection, spatial positioning and control of treatment time Table 11 is a list of the QA procedures and frequency Table 11: QA of remote afterloading brachytherapy units [3] 5.3.1 Calibration The source strength of LDR source and HDR source are determined by using a well ionization chamber or a thimble chamber However, the accuracy and precision of calibration for HDR sources using well ionization chamber has limitations due to the low efficiency and high signal currents 5.3.2 Verification of Source Position Verification of correct source positioning and sequencing can be 32 Comprehensive QA for Radiation Oncology accomplished by autoradiography The relative optical density may be valuable in qualitatively distinguishing between different sources 5.3.3 End effects While external beam units are adjusted against an internal timer and monitor unit, remote afterloading units are frequently calibrated against an independent clock One technique for measuring end effects is to affix a Farmer chamber in close contact with the applicator to obtain a high signal 5.3.4 Safety Because the sources may contain photon emitters of relatively high intensities and may emit significant dose rates near the patient, therefore, special cautions should be taken in caring for patient receiving brachytherapy Minimizing dose to hospital personnel and family is one potential advantage of remote afterloading devices Three common methods for reducing radiation exposure to personnel are (1) limiting the time of contact with patient, (2) increasing the distance from the patient, and (3) the use of protective barriers 33 Comprehensive QA for Radiation Oncology CHAPTER 6: QA OF CLINICAL ASPECTS In this chapter, the important components of clinical QA are described as peer review including new patient planning conference, chart review, film review and film type 6.1 New Patient Planning Conference New patient planning conference should be participated in by radiation oncologists, radiation therapists, dosimetrists and medical physicists For each patient, the prescribed dose, critical organ doses, possible patient positioning, possible field arrangements and special instructions should be examined Other areas which ought to be discussed are: the need for point dose calculations, the need for in vivo dosimetry where there is uncertainty in the calculational methods and the need for designed points where the cumulative dose is required 6.2 Chart Review The basic components of a patient chart should include: • Patient identification ( name, identity document, photograph) • Initial physical evaluation of patient and proper clinical information (diagnosis and stage of disease, history and physical, pathology report) • Treatment planning (simulator, setup construction, MU calculation, graphical plans, in vivo dostrimetry results, daily record, etc.) • Clinical assessment during treatment ( weight, blood count, dose to date) • Treatment summary and follow up ( summary of clinical problems, treatment delivery, patient’s tolerance, tumor response) • QA checklists Charts are recommended to be reviewed at least weekly, before the third fraction following the start of each new treatment field or field modification, or at the completion of treatment The chart review should be signed and dated by the reviewer Moreover, each department’s QA committee oversees the implementation of a program and all errors should be reviewed and discussed by the QA committee 34 Comprehensive QA for Radiation Oncology 6.3 Chart Check Protocol 6.3.1 Review of New or Modified Treatment Field The primary task of the chart checking is to identify any changes in treatment or new treatment fields since previous weekly chart review The chart reviewer should check and search for new prescriptions, new fields or field parameter modifications, MU changes, simulator and portal films, indication of modified fields, isodose distribution, etc Especially, the reviewer should alert to the parameters such as: wedge or wedge angle, SSD, SAD, interfield separation, number of field per fraction, treatment unit and modality, dose prescription Furthermore, having determined the new or modified treatment fields, it is necessary to review the specific areas of the chart, including treatment prescription, simulator instructions, isodose distributions, MU calculation, In vivo measurements and daily treatment record 6.3.2 Weekly Chart Review Along with review of new or modified treatment fields, weekly chart review also consists of review of previous fields and cumulative dose In review of previous fields, for each patient, the reviewer should determine: • The date of the previous weekly chart review • Whether the interval between chart reviews has been proper according to department policy • Whether the chart and the calculations have been reviewed by more than one physicist or dosimetrist • Whether the monitor unit calculations have been reviewed by a person who not accomplished the original calculation And in cumulative dose, the chart review should determine whether: • All doses have been correctly summed since previous chart review • The total dose to the prescription point exceeds the prescribed value The total dose to the prescription point will reach the total prescribed dose prior to the next weekly chart review 35 Comprehensive QA for Radiation Oncology 6.4 Film Review Two imaging techniques are utilizing to assess position and target volume, namely location using portal images and location using verification images 6.4.1 Portal Images The purposes of portal imaging are to verify that radiation field isocentre is correctly registered with respect to the patient’s anatomy and that the aperture has been properly produced and registered with respect to radiation field isocentre A portal image can be obtained using a relatively sensitive X-ray film exposed to only a small fraction of the daily treatment dose “Double exposure” image is a subcategory of portal film One exposure is obtained with treatment field aperture in place (with block or MLC) The second exposure is taken with the cerrobend blocks removed and the X-ray jaws opened 6.4.2 Ongoing and Verification Images An error in interpreting the films on the first day, a modification in the setup procedure, a change in the radiation therapist in the treatment, changes in patient anatomy can cause systematic deviations in the registration of radiation field Therefore, the recording and review of ongoing portal and verification images is an important aspect of comprehensive QA program Verification images are single exposure images These images record what occurred during treatment including the motion of the patient and the presence of radiation beam modified while double-exposure image cannot 36 Comprehensive QA for Radiation Oncology CONCLUSION The aim of comprehensive QA is to provide the organizational structure, responsibilities, procedures, processes and resources for assuring that the quality of patient management is what it should be The comprehensive QA program covers the quality of all aspects of patient care: services (e.g taking patient data, making appointments, diagnosis, treatment planning, treatment, and follow up), products (e.g customized beam blocks, immobilization devices, individualized compensators), equipment used (accelerators, simulators), psychological and the records of all aspects of diagnosis, planning, treatment and follow up My thesis emphasizes the physical aspects of QA and dose not attempt to discuss essentially medical issues But it by no means neglects issues in which the physical and medical issues intertwine, often in a complex manner QA activities cover a broad range, and the work of medical physicists in this regard extends into a number of areas in which the actions of radiation oncologists, radiation therapists, dosimetrists, accelerator engineer and medical physicists are important Therefore, QAC is established to oversee the QA program and the QAC have responsible of assisting the entire radiation oncology staff Since quality assurance plays such an important role in radiation oncology, hospitals or institutions should not ignore this part any more Especially, institutions need to develop training courses for staff that has expertise and skills for quality assurance 37 Comprehensive QA for Radiation Oncology REFERENCES Tiếng Việt [1] Nguyễn Xuân Kử, “Chương trình kiểm soát đảm bảo chất lượng xạ trị (QA-QC)”, “Cơ sở vật lý tiến xạ trị ung thư” NXB Y học, 2010 [2] Nguyễn Xuân Kử, “Những sai số thường gặp chương trình kiểm soát, đảm bảo chất lượng (QA-QC) xạ trị ung thư”, “Cơ sở vật lý tiến xạ trị ung thư” NXB Y học, 2010 English [3] “Comprehensive QA for Radiation Oncology: Report of AAPM Radiation Therapy Committee Task Group 40”, 1994 [4] AAPM (1984) “Physical aspects of quality assurance in radiation therapy,” American Association of Physicists in Medicine Report Series No.13 (American Institute of Physics, New York) [5] AAPM (1987) “Specification of brachytherapy source strength,” AAPM Rep No 21 (American Institute of Physic, New York) [6] AAPM (1993a) “Code of practice for accelerators Report of Task Group 45 of the Radiation Therapy Committee of AAPM” [7] AAPM (1993c) “Remote afterloading technology,” AAPM Rep.No.41 (American Institute of Physicists, New York) [8] AAPM (1993h) “Meterset calculations in radiotherapy Report of Task Group 51 of the Radiation Therapy Committee of AAPM” [9] Barendsen, G W (1982) “Dosefraction, dose rate and isoeffect relationships for normal tissue responses,” Int J Radiat Oncol Biol Phys.8, 1981-1997 [10] Drzymala, R E., Mohan, R., Brewster, L, Chu, J Goitein, M., Harms, 38 Comprehensive QA for Radiation Oncology W., and Urie, M (1991) “Dose volume histrograms,” Int J Radiat Oncol Biol Phys 21, 71-78 [11] Hanson, W F., Shalek, R J., and Kennedy, P (1991) “ Dosimetry quality assurance in the U.S from experience of the radiological physics center,” in Quality Assurance in Radiotherapy Physics, edited by G Starkschall and J Horton (Medical Physics Publishing Madison, WI), pp 255-279 [12] ICRU (1976) “Determination of absorbed dose in a patient irradiated by beams of x- or gamma-rays in radiotherapy procedures,: ICRU Rep.24, International Commission on Radiation Units and Measurement, Bethesda, MD [13] ICRU (1985) “Dose volume specification for reporting intracavitary therapy in gynecology,” ICRU Rep No 38, International Commision on Radiation Units and Measurement, Bethesda, MD [14] ICRU (1992) “Report of ICRU Working Group on Dose Specification and Reporting for Interstitial Brachytherapy” [15] ISCRO (1986) “Radiation oncology in integrated cancer management,” Report of the Inter-Society Council for Radiation Oncology [16] JCAHO (1992) “Quality Assurance Standards,” Joint Commission on the Accreditation of Healthcare Organizations: Radiation Oncology Services [17] Leunens, G., Van Dam, J., Dutreix, A., and Van der Schueren, E (1990) “Quality assurance in radiotherapy by in-vivo dosimetry 1: entrance dose measurements, a reliable procedure,” Radiother Oncol 17, 141-150 [18] Podmaniczky, K C., Mohan, R., Kutcher, G J., Kestler, C., and Vikram, B (1985) “ Clinical experience with a computerized record and verify system,” Int J Radiat Oncol Biol Phys 11, 1592-1537 39